Underwater explosive effects attenuator



April 26, 1966 M. SCHIMMEL UNDERWATER EXPLOSIVE EFFECTS ATTENUATOR 2 Sheets-Sheet 1 Filed April 1. 1964 INVENTOR.

MORRY L. SCHIMMEL BY M Ma 1.

April 1956 M. L. SCHIMMEL 3,248,072

UNDERWATER EXPLOS IVE EFFECTS ATTENUATQR Filed April 1. 1964 2 Sheets-Sheet 2 BLAST ENERGY AS A FUNCTION OF DISTANCE AND ENVIORMENT ENERGY lN.-LBS/IN.

O 2 4 6 8 IO SE NSOR DISTANCE INCHES FIGS.

INVENTOR. MORRY L. SCHI MMEL United States Patent 3,248,072 UNDERWATER EXPLOSIVE EFFECTS ATTENUATOR Morry L. Schimmel, University City, Mo., assignor to McDonnell Aircraft Corporation, St. Louis, Mo., a

corporation of Maryland Filed Apr. 1, 1964, SerrNo. 356,577 1 Claim. (Cl. 244-1) The present invention relates to attenuation of explosive effects, and more particularly the invention relates to attenuation of underwater explosive effects of explosive charges used for severance of structural members or separation of various structures from supports, and more specifically relates to'separating personnel capsules from a vehicle such as a submarine, a spacecraft, an aircraft or the like especially when escape action is required on entering or in the water.

The usual escape pod or capsule design of an airborne craft is such that the capsule is severed from the craft by an explosive charge shearing all support members of the capsule, and then the capsule is ejected from the craft by a rocket or similar device. A relatively simple technique is commonly used to effect escape pod severance from its 'craft. Such technique includes placing shaped charges about shear lines between the capsule and remainder of the aircraft or spacecraft. in positioning and locating the shaped charge much consideration is given to the safety of personnel and equipment, however, little consideration has been given to controlling blast energy dissipation or attenuation, especially in an underwater environment. This energy must be attenuated in order to prevent rupture of the escape pod structure.

The invention disclosed herein overcomes the difficulties of intensified blast eflect created by the approximate thousand-fold increase in efiiciency of blast energy transmission in water over air. In accordance with the invention, the explosive charge which may be a flexible linear shaped charge (FLSC), is surrounded or encased in an attenuator body which is made of a very low density material such as urethane foams. In particular, when FLSC explosive is used, the attenuator material may be used to encase the FLSC or to cover the shear line of the structure on the opposite side from the FLSC. Also, it may be desirable both to encase the FLSC and to cover the opposite side of the structure from the charge with the attenuator material to provide the minimum blast energy transmission especially for underwater escape action. Of course, the factor of prime importance in positioning the attenuation material is the direction of blast force with respect to personnel, equipment and escape pod confining surfaces. Hence, it is most desirable to attenuate the blast force near its origin in a location providing maximum attenuation with respect to the essential area of protection. The blast energy attenuation achieved by the invention in a marine environment approaches an order of magnitude greater than the usual value.

Moreover, by utilizing the attenuation materials and techniques appertaining to the invention, it is immaterial at What attitude the airborne craft enters the water or whether it is partly or completely'submerged.

It is, therefore, one of the principal objects of the present invention to provide a blast force attenuator device especially adapted to prevent excessive blast force transmission in a marine environment directed toward an airborne craft escape compartment such as to make escape procedure dangerous and ineffective.

Another object of the invention is to provide an explosive encasement of a low density material which is suitable to attenuate the blast force of the explosive with a greater efliciency than normal marine environment attenuation.

Another object of the invention is to provide an explosive severable escape compartment for an airborne craft which may be effectively activated with complete safety to personnel and compartment whether the craft be in air, partly in a marine environment or wholly submerged in the marine environment.

A further object of the invention is to provide an air- 7 borne craft escape compartment with a flexible linear shaped charge formed about a shear line in close proximity to the escape compartment contour, the shaped charge having a low density, blast force attenuator material thereabout to prevent damage to the escape compartment when the shaped charge is detonated while a portion of the escape compartment or pod is submerged in a marine environment.

A further object of the invention is to provide a flexible linear shaped charge embedded in a blast force attenuator material which is capable of multi-fold decreasing blast force energy transmission in a marine environment.

.Another further object of the invention is to provide an explosive charge embedded in a low density material which is eifective to produce a multi-fold decrease in blast force energy transmission compared to marine environment transmission.

A still further object of the invention is to provide an explosive force separable escape compartment for a vehicle which may require escape procedures under conditions generating marine environment blast energy transmission wherein a low density material is provided sur-- rounding the explosive to effect a multi-fold decrease in blast energy transfer to the marine environment.

A still further object of the invention is to provide a low density material encasing an explosive charge on one side of an explosive blast force shearable structure and merely the low density material on the opposite side of the structure.

Another further object of the invention is to provide a low density cellular material on the opposite side of an explosive force shearable structure from a shaped charge explosive directed to shear such structure.

These and other objects and advantages of the presentinvention will be readily apparent to those skilled in the art from the description herein taken in conjunction'with the appended claim and the drawings wherein:

FIGURE 1 illustrates in a fragmentary view the nose section of an aircraft and escape compartment.

FIGURE 2 illustrates a fragmentary sectional view of the escape compartment using one form of the invention.

, FIGURE 3 depicts a fragmentary sectional view of the inventive device on the opposite side of a shearable structure from a shaped charge explosive used to separate the escape compartment.

FIGURE 4 depicts the attenuator material appertaining to the invention is use on both sides of the shearable structure at the separation plane of the escape pod.

FIGURE 5 is a graph ilustrating the relative eflectiveness of the invention in attenuation of blast energy.

Referring to FIGURE 1 there is illustrated the nose section of an aircraft generally designated 10. The nose section has an escape compartment or pad .20 which is a hermetically sealable structure. The pod 20 consists of surface structure 21 mounting a windshield 22 and a retractable canopy structure 23. The pod 20 mounts seat (FLSC) is placed very near the escape compartment structure as depicted by dashed lines 28.

Patented Apr. 26, 1966 In FIGURE 2 the fragmentary sectional view taken along line 22 of FIGURE 1 illustrates details of one embodiment of the invention. Capsule or pod 20 is formed partly by floor panel 30 attached to superstructure 31 by means not illustrated. Likewise, surface skin 21 is attached to superstructure 31 by rivets 3-2. Nose section body or skin 15 joins superstructure 31 along rivet line 33. Rivet line 33 supports a bracket 34 containing a FLSC 35 embedded in low density, cellular material 36. The bracket 34 and cellular material 36 position FLSC 35 to superstructure 31. FLSC 35 is initiated under escape procedures by a detonation transmission line which is usually activated by a manual lever or handle (not shown). The transmission line terminates with detonator 37. The major severing force of the explosion of FLSC 35 is directed against wall 39 of superstructure 31. This construction and arrangement places the cellular material 36, which attenuates the blast energy transfer, between the escape pod 20 and the shearable structure 39, and provides blast protection to the escape pod fioor 30.

In FIGURE 3 another fragmentary view of the escape compartment 20 illustrates interposing attenuator material of the invention between the explosive charge and escape pod. superstructure 41 forms part of the floor of escape compartment 20. A portion of floor panel 30 is attached to superstructure 41 by means not shown. Also, a portion of aft bulkhead or panel 42 is attached to structure 41 by rivets 43. Superstructure 41 is attached 'by rivets 44 to shearable support 45 which is at a downward angle from the compartment 20 floor. A flexible linear shaped charge (FLSC) 50 is provided in a conforming holder 51 which has an extension 52. The holder 51 with FLSC 50 is positioned on the underside of support 45, away from the floor of capsule 20. On the side of support 45 opposite FLSC 50 there is provided a housing 53 with an extension bracket 54 projecting therefrom. Within housing 53 a low density, cellular material 55 is provided. Housing 53 and holder 51 are attached to support 45 by rivets 49. FLSC 50 on initiation under escape procedures severs support 45. The major blast force of FLSC 50 is directed against support 45 and into cellular material 55. Thus, the major energy of FLSC 50 is attenuated by material 55 which is positioned between the escape housing 20 and the FLSC 50 thus aifording maximum capsule safety.

FIGURE 4 depicts another embodiment of the invention in which the FLSC is embedded in a low density. cellular material and the blast force of the FLSC is directed toward a shearable structure with low density, cellular material on the. side opposite such FLSC. This embodiment is most useful for severing underfloor support structure where maximum capsule danger is likely. The floor section 30 is supported by a shearable plate 61 attached to bracket 62. The rivets 63 hold floor panel 30 to plate 61 and aflixes a clamp bracket 64 along one side of plate 61. The bracket 64 is filled with low density material 65. On the side of plate 61 opposite bracket 64, rivets 66 afiix holder 67 to plate 61 and attach both to bracket 62. Within holder 67, low density material 69 embeds flexible linear shaped charge 68 with its b-last force directed toward shearable panel 61 and low density material 65.

FIGURES 1-4 are illustrative of the various escape compartment structural techniques used to affordseverance between the escape pod and remainder of the craft. The low density material used is preferably Lockfoam P-502 (available from Lockheed Aircraft), but may be NOPCO Foam G203. Furthermore, the foam density is preferably 2 lbs. per cu. ft. Best results are obtained for underwater blast force attenuating by using a closed cell, low density foam.

In order to best illustrate the effectiveness of the invention, numerous tests were conducted. FIGURE is a graph showing energy (in.-lbs./in. as a logarithmic function of distance from a sensor for various underwater flexible linear shaped charge explosions. All FLSC charges for Curves A, B, C and D were 20 grains per foot. For Curve A, the FLSC was taped directly against the target, andafter initiation the energy level at varying distances from the charge was recorded. The data on curve B were recorded for the identical FIBC weight as Curve A, but a Lockfoam P502 holder of 0.50 sq. in. cross-sectional area was used to attenuate the blast force. The data for Curve C were recorded for the identical FLSC weight as Curve B, but the holder was 3.12 sq. in. cross-sectional area. The data for Curve D were taken with the FLSC attached to the target and exposed in an air environment. Again the FLSC was 20 grains per foot. The data of Curves A, B and C were obtained for underwater explosions. Also, Curves B and C quantitative attenuation, i.e., the greater the foam cross-sectional area surroundin a given FLSC or other explosive the more attenuation.

Upon inspection of the curves in FIGURE 5, it will be appreciated that the exponental decay or dissipation of energy from the FLSC is such that low density foam surrounding the explosive or interposing the energy path near the escape pod shear line explosive effectively provides for safety whether or not the escape procedure is necessary with the aircraft submerged in a marine environment.

It should be appreciated that the invention has been disclosed with various embodiments and preferred material and structure, and such description will suggest various modifications and changes to those skilled in the art, and such are within the intent and scope of the invention which is limited necessarily only to the scope of the appended claim.

What is claimed is:

An emergency escape pod mounting and severing mechanism for aircraft which can be activated under any conditions of air and water environmental medium around the aircraft and escape pod with safety to the escape pod comprising a support means. in the aircraft including shearable structure to releasibly secure said escape pod in the aircraft, said shearable structure extending away from portions of the escape pods outer surface, a shaped charge mounted coexten-sively on said shearable structure, said shaped charge on detonation effective to sever said shearable structure along its entirety, a first portion of low density, cellular material covering said shaped charge and contiguous shearable structure, and a second portion of low density cellular material covering said support structure on the side opposite said shaped charge, said first portion of low density, cellular material separating said shaped charge and contiguous shearable structure from said environmental medium. around the aircraft and escape pod, said second portion of low density, cellular material separating shearable structure opposite said shaped charge from said environmental medium around the aircraft and escape pod, said first and second portions of said cellular material effective to provide a uniform attenuating environment for the blast pressure of said shaped charge sufficient to avoid damage of the escape pod by said blast .pressure passing through said environmental medium toward said escape pod.

References Cited by the Examiner UNITED "STATES PATENTS 2,543,057 2/1951 Porter 102--24 2,797,892 7/1957 Ryan 102-24 X 2,849,953 9/1958 Delacous 102-24 X 3,067,973 12/1962 Halsey et a1.

3,107,641 10/ 1963 Haynes.

3,108,540 10/1963 Fletcher 10249 BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL W. ENGLE, Examiner. 

